VBSCRIPT VARIABLES AND DATATYPES

What Is a Variable?

A variable is a convenient placeholder that refers to a computer memory location where you can store program information that may change during execution

Declaring Variables

We declare variables explicitly in our script using the Dim statement, the Public statement, and the Private statement. We declare multiple variables by separating each variable name with a comma. For example: Dim Top, Bottom, Left, RightWe can also declare a variable implicitly by simply using its name in our script. Because we may misspell the variable name in one or more places, causing unexpected results During execution. For that reason, the Option Explicit statement is available to require explicit declaration of all variables. The Option Explicit statement should be the first statement in the script.

Option explicit:

When We use the Option Explicit statement, you must explicitly declare all variables using the Dim, Private, Public, or ReDim statements. If we attempt to use an undeclared variable name, causing an error occurs.

Naming Restrictions

Variable names follow the standard rules for naming anything in VBScript. A variable name:

Must begin with an alphabetic character. Cannot contain an embedded period. Must not exceed 255 characters. Must be unique in the scope in which it is declared.

Assigning Values to Variables

Values are assigned to variables creating an expression as follows: the variable is on the left side of the expression and the value you want to assign to the variable is on the right. For example: B = 200

DATATYPES

What Are VBScript Data Types?

VBScript has only one data type called a Variant. A Variant is a special kind of data type that can contain different kinds of information, depending on how it's used. Because Variant is the only data type in VBScript, it's also the data type returned by all functions in VBScript.

At its simplest, a Variant can contain either numeric or string information. A Variant behaves as a number when you use it in a numeric context and as a string when you use it in a string context. That is, if you're working with data that looks like numbers, VBScript assumes that it is numbers and does the thing that is most appropriate for numbers. Similarly, if you're working with data that can only be string data, VBScript treats it as string data. Of course, you can always make numbers behave as strings by enclosing them in quotation marks (" ").

Variant Subtypes

The following table shows the subtypes of data that a Variant can contain.

Subtype Description

Empty Variant is uninitialized. Value is 0 for numeric variables or a zero-length string ("") for string variables.

Null Variant intentionally contains no valid data.

Boolean Contains either True or False.

Byte Contains integer in the range 0 to 255.

Integer Contains integer in the range -32,768 to 32,767.

Currency -922,337,203,685,477.5808 to 922,337,203,685,477.5807.

Long Contains integer in the range -2,147,483,648 to 2,147,483,647.

Single Contains a single-precision, floating-point number in the range -3.402823E38 to -1.401298E-45 for negative values; 1.401298E-45 to 3.402823E38 for positive values.

Double Contains a double-precision, floating-point number in the range -1.79769313486232E308 to -4.94065645841247E-324 for negative values; 4.94065645841247E-324 to 1.79769313486232E308 for positive values.

Date (Time)

Contains a number that represents a date between January 1, 100 to December 31, 9999.

String Contains a variable-length string that can be up to approximately 2 billion characters in length.

Object Contains an object.

Error Contains an error number.

Operator Precedence

When several operations occur in an expression, each part is evaluated and resolved in a predetermined order called operator precedence. You can use parentheses to override the order of precedence and force some parts of an expression to be evaluated before others. Operations within parentheses are always performed before those outside. Within parentheses, however, standard operator precedence is maintained. When expressions contain operators from more than one category, arithmetic operators are evaluated first, comparison operators are evaluated next, and logical operators are evaluated last. Comparison operators all have equal precedence; that is, they are evaluated in the left-to-right order in which they appear. Arithmetic and logical operators are evaluated in the following order of precedence.

ArithmeticDescription Symbol

Exponentiation ^

Unary negation -

Multiplication *

Division /

Integer division \

Modulus arithmetic Mod

Addition +

Subtraction -

String concatenation &

Comparison

Description Symbol

Equality =

Inequality <>

Less than <

Greater than >

Less than or equal to <=

Greater than or equal to >=

Object equivalence Is

LogicalDescription Symbol

Logical negation Not

Logical conjunction And

Logical disjunction Or

Logical exclusion Xor

Logical equivalence Eqv

Logical implication ImpWhen multiplication and division occur together in an expression, each operation is evaluated as it occurs from left to right. Likewise, when addition and subtraction occur together in an expression, each operation is evaluated in order of appearance from left to right.

The string concatenation (&) operator is not an arithmetic operator, but in precedence it falls after all arithmetic operators and before all comparison operators. The Is operator is an object reference comparison operator. It does not compare objects or their values; it checks only to determine if two object references refer to the same object.

The logic of OR is that if at least one of the inputs are True, the output is true;

True OR True = True

True OR False = TrueFalse OR True = TrueFalse OR False = False

XOR only returns True if one and only one of the inputs is True.

True Xor True = FalseTrue Xor False = TrueFalse Xor True = TrueFalse Xor False = False

Imp returns false if first one is true and second one false except this it returns true.

True imp True = TrueTrue imp False = FalseFalse imp True = TrueFalse imp False = True